"expected a string enum" error when attempting to add text strip
You are passing a string into the function instead of the actual arguments. Since effect_strip_add doesn't have any function signature that takes a string as first arguments you're getting the TypeError exception. The concept of keyword arguments is explained in this section of the Python docs.

The proper way of calling the function is passing each of the arguments.

bpy.ops.sequencer.effect_strip_add(frame_start=fStart, frame_end=fEnd, channel=tChan, type='TEXT')




bpy.ops.sequencer.effect_strip_add is documented in Blender 2.8 Python API with the following function signature:


  bpy.ops.sequencer.effect_strip_add(frame_start=0, frame_end=0,
  channel=1, replace_sel=True, overlap=False, type='ALPHA_OVER',
  color=(0.0, 0.0, 0.0))
  
  Add an effect to the sequencer, most are applied on top of existing
  strips
  
  Parameters:
  
  
  frame_start (int in [-inf, inf], (optional)) – Start Frame, Start frame of the sequence strip 
  frame_end (int in [-inf, inf], (optional)) – End Frame, End frame for the color strip 
  channel (int in [1, 32], (optional)) – Channel, Channel to place this strip into
  replace_sel (boolean, (optional)) – Replace Selection, Replace the current selection 
  overlap (boolean, (optional)) – Allow Overlap, Don’t correct overlap on new sequence strips 
  type (enum in ['CROSS', 'ADD', 'SUBTRACT', 'ALPHA_OVER', 'ALPHA_UNDER', 'GAMMA_CROSS', 'MULTIPLY', 'OVER_DROP', 'WIPE', 'GLOW',
  'TRANSFORM', 'COLOR', 'SPEED', 'MULTICAM', 'ADJUSTMENT',
  'GAUSSIAN_BLUR', 'TEXT', 'COLORMIX'], (optional)) – Type, Sequencer
  effect type
  
  
  CROSS Crossfade, Crossfade effect strip type.
  ADD Add, Add effect strip type.
  SUBTRACT Subtract, Subtract effect strip type.
  ALPHA_OVER Alpha Over, Alpha Over effect strip type.
  ALPHA_UNDER Alpha Under, Alpha Under effect strip type.
  GAMMA_CROSS Gamma Cross, Gamma Cross effect strip type.
  MULTIPLY Multiply, Multiply effect strip type.
  OVER_DROP Alpha Over Drop, Alpha Over Drop effect strip type.
  WIPE Wipe, Wipe effect strip type.
  GLOW Glow, Glow effect strip type.
  TRANSFORM Transform, Transform effect strip type.
  COLOR Color, Color effect strip type.
  SPEED Speed, Color effect strip type.
  MULTICAM Multicam Selector.
  ADJUSTMENT Adjustment Layer.
  GAUSSIAN_BLUR Gaussian Blur.
  TEXT Text.
  COLORMIX Color Mix.
  
  color (float array of 3 items in [0, 1], (optional)) – Color, Initialize the strip with this color (only used when type=’COLOR’)